virtualbox.org

I am running virtualbox on windows 7. I have two questions concerning memory assignment for guest machines. I have a 500 gb hard drive and 12 gigs of ram. When I create a Linux guest what is a safe amount of ram to assign the guest machine? Also if I am running only one guest machine at a time, how hard is that going to effect my host machine? Last question what is usually the normal amount of ram assigned a 64 guest machine and a 32 bit machine? Thank you in advance.

There is no simple answer to those questions, just as there is no simple answer for the same questions about physical machines. It depends entirely on what you expect the machine to do.

Start with the default settings for memory and disk size and adjust them if they don't suit your usage.